Limited studies indicate an important role of mitochondrial-derived factors in the control of the cerebral circulation beyond effects which are related to energy supply. Thus, factors which depolarize mitochondria and/or augment the release of ROS from mitochondria activate signaling pathways leading to net dilation of cerebral arteries. Furthermore, our preliminary data indicate that mitochondrial influences are adversely affected by insulin resistance (IR). Our overall hypothesis is that mitochondrial-derived influences are key regulators of cerebral vascular tone but are compromised by IR. Two Specific Aims will test our hypotheses and speculations in rats: Aim 1. Examination of the roles of mitochondrial-derived influences in mediating responses of cerebral arteries. We will: A) Determine the relationship among cerebral arterial vasodilation, mitochondrial depolarization, kinase activation, and mitochondrial ROS production. B) Elucidate the mechanisms of dilation due to mitochondrial depolarization, kinase activation, ROS generation, and plasmalemmal calcium-activated potassium channel opening. C) Evaluate the inter-relationships of mitochondrial-derived factors produced in endothelium and VSM cells in mediating integrated dilator responses. D) Determine whether preconditioning, induced by prior activation of mitochondrial-derived mechanisms, alters subsequent cerebrovascular responses to mitochondrial-derived products. E) Explore the relationship between physiological stimuli and mitochondrial activation. Aim 2. Investigation of the effects of IR on mitochondrial-derived influences on cerebral arteries. We will: A) Examine whether IR attenuates dilator responses of cerebral arteries dependent upon mitochondria-derived signaling pathways. B) Determine the mechanisms by which IR reduces the responsiveness of cerebral arteries to mitochondrial-derived influences. C) Examine whether treatment of animals with statins restores normal responsiveness to mitochondrial-derived stimuli in IR. We expect that our results will lead to the improved treatment of patients suffering from cerebrovascular disease.